Mild detergent compositions



United States Patent 3,223,647 MliiiD DETERGENT CGMPOSHTIONS Howard F. Drew, North Coiiege Hill, and Jack G. Voss, Wyoming, Uhio, assignors to The Procter 8: Gamble @ompany, Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed Apr. 20, 1959, Ser. No. 807,333 11 Claims. (Cl. 252-137) This invention relates to combinations of synthetic detergents which have superior mildness characteristics. More particularly it relates to combinations of certain alkyl benzene sulfonates and tertiary amine oxides, which combinations are mild in their action toward the skin.

Alkyl benzene sulfonates having alkyl radicals ranging from about 9 to about 15 carbon atoms are widely used as household synthetic detergents. They are economical, and have good detergency, foaming, solubility, odor and color characteristics. However, in view of present day emphasis on mildness in detergent products and in view of published information (Schwartz, Perry and Berch, Surface Active Agents and Detergents, vol. ll, page 377) that these synthetics are less mild than soap, it is desirable that these alkyl benzene sulfonates be rendered as mild as possible to the human skin.

Tertiary amine oxides, represented by the chemical formula (the oxygen being attached to the nitrogen by a semipolar bond), and conventionally indicated by the formula R R R N+ 0, wherein R is an alkyl radical containing about 10 to about 18 carbon atoms and R and R are each lower alkyl radicals, also are very efficient synthetic detergents with excellent detergency and foaming characteristics. However, like the above-mentioned alkyl benzene sulfonates, it is desirable that these amine oxides be rendered milder to the human skin.

The relative mildness to the human skin of the aforementioned alkyl benzene sulfonates and amine oxides can be determined by exaggerated exposures with test animals. In tests of extreme severity conducted on guinea pigs, for example, the alkyl benzene sulfonates and the amine oxides when used alone, cause a thickening of the skin of the test animal, usually accompanied by dryness and cracking of the skin.

It is an object of this invention to provide a composition containing a mixture of synthetic detergents which has excellent detergency characteristics and has a mildness to the skin markedly superior to the mildness of either of the component detergents alone.

It is another object of this invention to provide a cleansing composition containing a tertiary amine oxide and an alkyl benzene sulfonate, which are mildness additives for each other, and each of which is a highly efiicient detergent and foaming agent.

It was found that certain mixtures of the amine oxides and alkyl benzene sulfonates described above exhibit superior and unexpected mildness characteristics. In certain ranges, and under comparable conditions of exposure, mixtures of these two detergents in solution are milder to the skin than either one alone. The aforementioned thickening, dryness and cracking of the skin of test animals under exaggerated exposures are markedly reduced and in some cases disappear. This mildness effect is very advantageous since combinations of the alkyl benzene sulfonates and amine oxides in the compositions of the present invention are very efficient, good foaming detergents. For example, if it is desired to make milder either the alkyl benzene sulfonate or the amine oxide, one of the ingredients can be combined with the other as hereinafter described with no reduction in the desired detergency or sudsing on the basis of the total detergent present, since both ingredients are excellent in these properties.

The cleansing compositions of this invention having superior mildness characteristics comprise mixtures of alkyl benzene sulfonates having alkyl radicals ranging from about 9 to about 15 carbon atoms and tertiary amine oxides, having the formula R R R N O wherein R is an alkyl radical containing from about 10 to about 18 carbon atoms and R and R are each methyl, ethyl or propyl radicals, the ratio of the respective ingredients being in the range of about 20:1 to about 1:5, preferably about 10:1 to about 1:2.

The alkyl benzene sulfonates in the compositions of this invention are the water soluble salts, such as the alkali metal (e.g. sodium, potassium and lithium), ammonium and substituted ammonium (e.g. triethanolamine) salts, of sulfonated alkyl benzene in which the alkyl radicals range from about 9 to about 15 carbon atoms. Alkyl benzene sulfonates usually contain mixtures of alkyl radicals in this range. The preferred alkyl benzene sulfonate is one in which the alkyl radicals in the mixture average about 12 carbon atoms and are derived from a polypropylene which is predominantly tetrapropylene. This alkyl benzene sulfonate is hereinafter referred to as dodecyl benzene sulfonate and is most commonly used as a sodium salt.

Alkyl benzene sulfonates can be produced in a number of ways. The usual processes involve first the preparation of a satisfactory source for the alkyl component such as an olefin, e.g. polypropylene, or an alkyl halide, e.g. chlorinated kerosene. Alkyl benzene is formed by condensing the olefin or alkyl halide with benzene in a reaction of the Fried-el-Crafts type using a catalyst such as Alclg or HP. The alkyl benzene is then sulfonated, purified, converted to the desired salt and worked up to the desired form, e.g. powder, granule or paste. The manufacture of alkyl benzene sulfonates is described in the Journal of the American Oil Chemists Society, 35, 520 24 and 528-31 (1958).

The tertiary amine oxides in the compositions of this invention have the formula R R R N O wherein R is an alkyl radical containing from about 10 to about 18 carbon atoms, and R and R are each methyl, ethyl or propyl radicals. If R is shorter in chain length than about 10 carbon atoms, the solubility of the resulting amine oxide is reduced. If R is longer in chain length than about 18 carbon atoms, .the solubility of the resulting amine oxide is reduced to an undesirable point for detergency purposes. Amine oxides in which R, contains 12 to 16 carbon atoms have preferred solubility, foaming and detergency characteristics, particularly when R is a straight, saturated chain. It R and R are longer in chain length than 3 carbon atoms, the resulting amine oxide is not sufficiently soluble to be desirable as a detergent. Those higher alkyl tertiary amine oxides in which R and R are methyl radicals also have preferred detergen-cy, solubility and foaming characteristics for use in this invention. The lauryl dialkyl amine oxides and those tertiary amine oxides in which the R alkyl radicals are predominantly the mixture of lauryl and myristyl radicals found in fractionated coconut oil fatty alcohol are particularly desirable compounds in the compositions of the present invention.

The higher alkyl tertiary amine oxides of this invention can be produced by oxidizing higher alkyl tertiary amines with an oxidizing agent such as hydrogen peroxide or Caros reagent (ammonium or potassium persulfate dissolve-d in concentrated sulfuric acid). Higher alkyl tertiary amines can be produced by alkylating a secondary amine; for example, lauryl dimethyl amine can be produced by reacting dimethyl amine with lauryl alcohol or a derivative thereof such as lauryl iodide. Examples of the higher alkyl groups in the tertiary amine oxides which can be used in the compositions of this invention include primary alkyl groups such as cetyl and oleyl groups which are derived from fats and oils or petroleum derived olefins, secondary alkyl groups such as an m-methyl pentadecyl group derived from an a-olefin, substituted alkyl groups such as a 2 hydroxylauryl group, and non-aromatic interrupted alkyl groups such as a carb-amide substituted alkyl group. Methods for making amine oxides are described in British Patent No. 437,566.

Examples of amine oxides which can be used in preparing the compositions of the present invention are:

Lauryl dimethylamine oxide Myristyl d-imethylamine oxide Cetyl dimethylamine oxide Z-hydroxylauryl dimethyla-mine oxide u-M-ethylundecyl dimethylamine oxide Oleyl dimethylamine oxide Lauryl methyl ethyl amine oxide Lauryi diethylamine oxide Z-diethyl amino ethyl lauramide oxide Myristyl diethylamine oxide Cetyl diethylamine oxide a-Met'hylpentadecyl diethylamine oxide Oleyl diethylamine oxide Myristyl ethyl propyl amine oxide Lauryl dipropylamine oxide Myristyl dipropylamine oxide Cetyl dipropylamine oxide Cetyl methyl propyl amine oxide Coconut alkyl dime'thylamine oxide wherein the higher alkyl radicals are predominantly the mixture of lauryl and myristyl radicals found in coconut oil fatty alcohol (such a mixture can be obtained by taking the middle cut of fractionated coconut oil fatty alcohol) The unexpected mildness resulting from the combination of alkyl benzene sulfonates with amine oxides in accordance with the present invention appears to be specific only to the compounds designated. For example, when the aforementioned tertiary amine oxides were mixed with the salts of sulfated coconut oil fatty alcohols and tested for mildness, the mixtures were not significantly milder. Coconut oil alkyl sulfates, like alkyl benzene sulfonates, are widely used synthetic detergents which reportedly could be made mild-er.

In the testing of detergent compounds and compositions for mildness and for the unexpected mildness effect, skin is contacted by immersion or other means with a solution of the detergent under standardized conditions as more fully described 'below. A 1 to scale is used to rate the effects of prolonged exposure on the skin. Grade 10 represents ideal or perfect skin (soft, smooth and flexible) and the effect of a theoretically perfectly mild detergent; grade 1 represents severely irritated skin. Other values represent gradation-s of severity between these extremes. Grade 1 in a guinea pig immersion test indicates severely thickened, dry, cracked and bleeding skin, i.e. extreme irritation. Grade 1 in exaggerated tests on human subjects indicates severe redness and dryness of the skin. Thus, the exaggerated exposure tests on animals are much more extreme than those conducted on human subjects.

It was found that there is a'good correlation between the results of exaggerated exposure tests on animals and the results of normal use tests on humans, and that the former can be relied on to grade the relative mildness of detergents toward the human skin. This correlation was determined in the following manner. A series of standardized, graded guinea pig immersion tests were run on each of thirteen detergent compositions and on the basis of these results the compositions were rated in order of mildness. All compositions were within the normal range of mildness exhibited by washing compositions in use for many years. The order of mildness on humans was determined by extensive tests. A panel of about 300 housewives was used for each of the thirteen detergent compositions. The women were given the compositions in unprinted cartons identified only by a letter such as A or B, and were asked to use them regularly in dishwashing. The womens hands were examined by physicians before the use of the composition was started and again after about 2 weeks use of the composition. The examinations were usually made at least an hour after the use of the detergent composition, so that any temporary effect of hand immersion was not visible. The women were asked to use the compositions for all general household use, dishwashing being the most important.

On the basis of physicians ratings on the effect of the detergent compositions on the hands of the users, the thirteen compositions were arranged in order of mildness. The rank order correlation (see pages 87 of An Outline of Statistical Methods, Arkin & Colton, 4th E., Barnes & Noble) w N(N -1) (wherein p is the measure of correlation, D is the difference between the two ranks given for each detergent composition, and N is the number of compositions) was computed for the guinea pig tests vs. the doctors rating; p was +.88. In this type of correlation, a perfect correlation is +1.0; a complete reverse order disagreement calculates at l.0. Thus, a value of +.88 enables us to estimate relative human hand skin mildness from highly exaggerated guinea pig immersion tests.

As used in the following examples, the graded guinea pig immersion tests consist of immersing the animal up to the thorax in the test solutions at 37 C. for a 4 /2 hour period per day for 3 consecutive days. The animals are graded 3 days after the last immersion. The grades given in the examples are the average of the results on not less than three animals.

It will be understood by those with experience in biological experiments that there is variation in the reactions of individuals, within a group, to exposure to chemical solutions; this is true whether the individuals are guinea pigs or humans.

Example I The following aqueous solutions were compared in graded guinea pig immersion tests:

*Ungraded but extremely irritating.

A significant unexpected mildness effect is apparent in the solutions of mixtures of the above alkylbenzene sulfomate and amine oxide in a 2:1 ratio as compared to solutions in equal concentration, of the individual detergents alone.

Example 11 The following aqueous solutions were compared in graded guinea pig immersion tests:

Test Solutions Ratio, Alkylbenzene Sutton ate: Grade Percent Sodium Percent Lauryl Amine Oxide Dodeeyl Ben- Dimethyl Amine zene Sulfonate Oxide Example III The following aqueous solutions were compared in graded guinea pig immersion tests.

Ratio, Alkylbenzene Sulfonate: Amine Oxide Test Solution Grade 0.2% sodium dodeeyl benzene sultan-ate" 0.2% sodium alkyl benzene sult'onate (the alkyl group being derived from a mixture of straight chain olefins averaging 12 carbon atoms).

0.2% myristyl dimethyl amine oxide..

0.2% cetyl dimethyl amine oxide 0.2% oleyl dimethylamine oxide-..

0.2% 2-hydroxylauryl dimethyl amine x1 e. 0.2% 2-diethyl amino ethyl lauramide 0x1 e. 0.2% sodium dodeeylbenzene sulionate plus 0.1% myristyl dilnethyl amine ox e.

0.2% sodium dodeeylbenzene sultonate plus 0.1% cetyl dimethyl amine oxide.

0.2% sodium dodeeylbenzene sulfonate plus 0.02% cetyl dirnethyl amine oxide.

0.2% sodium alkyl benzene sulionate (the alkyl group being derived from a mixture of straight chain olefins averaging 12 carbon atoms) plus 0.1% lauryl dimethyl amine oxide.

0.2% sodium dodeeylbenzeue sulionate plus 0.1% 2-hydroxy1aury1 dimethylamine oxide.

0.2% sodium dodeeylbenzene sulionate plus 0.1% oleyl dimethylarnine oxide.

0.2% sodium dodecyl benzene sulionate plus 0.1% 2-diethyl amino ethyl lauramide oxide.

" Ungraded but extremely irritating.

It is apparent from the results set forth in Examples 11 and III that an unexpected mildness effect of mixtures of alkylbenzene sulfonates and tertiary amine oxide in this invention exists in the ratio range of these compounds of about 20:1 to about 1:5 and that the best mildness effects are seen in the ratio range of about 10:1 to about 1:2.

To illustrate that the amine oxides described in this invention do not appear to exert a significant unexpected mildness effect with other synthetic detergents which reportedly could be made milder, the following aqueous solutions were tested in a graded guinea pig immersion test.

Test solution: Grade 0.2% sodium salt of sulfated coconut oil fatty alcohol 0.2% sodium salt of sulfated coconut oil fatty alcohol+0.l% lauryl dimethyl amine oxide 5 6 Example IV An exaggerated arm washing exposure test was conducted on human subjects using two 10% solutions (A and B) of a granular detergent having the following compositions:

Percent Sodium dodecylbenzene sulfonate 17.5 Sodium tripo-lyph-osphate 50.0 Sodium sulfate 16.0

Sodium silicate solids having an SiO- :Na O ratio of 1.621 6.0 Monoethanolamide of coconut oil fatty acids 3.0 Moisture 7.5

Solution A consisted of the granular detergent composition alone. To Solution B an amount of lauryl dimethyl amine oxide equal to 10% by weight of the detergent composition in solution was added. The solutions were used at 105 F. Ten human subjects participated in the test. The inner aspects (inside) of each elbow of each subject were Washed with the solutions, one aspect with Solution A, the other with Solution B. The test consisted of rubbing the aspects for 30 seconds with a 4 inch square terry cloth wash cloth saturated with the test solution. The solution was allowed to remain on the subjects arm for an additional 30 seconds and the arm was then blotted dry. This washing test was conducted on each subject three times daily, morning, midday and afternoon, for three days. The subjects were graded after the final washing on a l to 10 scale as described above.

The following results were obtained, with the grade being the average of 10 subjects.

Grade Solution A 7.4 Solution B (containing added amine oxide) 9.1

Comparable to soap based laundry detergents.

It has been observed that a solution of a mixture of about equal parts of sodium dodecyl benzene sulfonate and lauryl dimethyl amine oxide effects no thickening and cracking of the skin of animals characteristic of the individual components alone, even in repeated, severe and exaggerated guinea pig exposure tests.

The mild mixtures of alkyl benzene sulfonates and amine oxides in the compositions of this invention are useful as detergents per se or in combination with any of the usual synthetic detergent adjuvants, builders, diluents and additives to produce mild detergent products such as heavyor light duty detergent granules, heavy and light duty liquid detergents, shampoos or detergent bar-s.

The mildness characteristics of the mixtures of alkyl benzene sulfonates and amine oxides of the present invention are useful in any detergent or cleansing composition which comes in contact with the skin in an aqueous medium. Detergent compositions containing the synthetic detergent mixture of this invention can comprise from about 0.5% to of the mixture as an essential detergent and sudsing component depending on the end use. For example, a scouring cleanser can contain as little as about 0.5% of the detergent mixture of this invention or a dry granular detergent composition comprising 100% of the mixture can be used to make a washing solution. In each case the composition containing the mixture of the invention is milder to the skin during use than an equal amount of either of the individual components of the mixture alone. Detergent compositions usually contain about 5% to about 50% synthetic detergent, i.e. the mixture of alkyl benzene sulfonates and amine oxides described in this invention.

Amine oxides are advantageously combined with alkyl benzene sulfonates not only for the unexpected mildness which is effected in the combination but for additional qualities which amine oxides impart to alkyl benzen sulfonate compositions.

The mixtures of alkyl benzene sulfonates and amine oxides of this invention are better solubilizers of calcium Example V A mild, heavy-duty, granular detergent composition was made by mixing together the following ingredients:

10 parts sodium dodecyl benzene sulfonate 10 parts lauryl dimethyl amine oxide 50 parts sodium tripolyphosphate 30 parts sodium sulfate The heavy duty detergency of this composition is excellent.

Example VI A mild, light-duty, granular detergent composition of excellent efficiency is made by mixing together the following ingredients:

25 parts potassium dodecyl benzene sulfonate parts cetyl diethyl amine oxide 45 parts sodium sulfate 15 parts sodium tripolyphosphate Example VII A mild efiicient liquid dishwashing detergent which foams well is made by mixing together the following ingredients:

15 parts ammonium dodecyl benzene sulfonate 15 parts lauryl methyl ethylamine oxide 10 parts ethanol 60 parts water Example VIII A mild efl'icient detergent toilet bar is made by dry mixing, milling, extruding and stamping into a bar the following ingredients:

parts sodium dodecylbenzene sulfonate 5 parts coconut alkyl dimethyl amine oxide in which the higher alkyl radicals are predominantly the mixture of lauryl and myristyl radicals found in fractionated coconut oil fatty alcohol 10 parts of coconut oil soap 50 parts tallow soap 15 parts moisture Example IX A mild shampoo with excellent foaming characteristics is made by mixing together the following ingredients:

10 parts triethanolamine dodecyl benzene sulfonate 10 parts lauryl dimethyl amine oxide 80 parts water Example X A mild scouring cleanser which foams and cleans well is made by mixing together the following ingredients:

85 parts silica flour 13 parts trisodium phosphate 1 part sodium dodecylbenzene sulfonate 1 part myristyl diethylamine oxide What is claimed is:

1. A composition capable of synergistic mildness when used as an active ingredient in a detergent composition, said composition being a mixture-of a water soluble alkyl benzene sulfonate having an alkyl radical ranging from about 9 to about 15 carbon atoms and a tertiary amine oxide having the formula R R R O wherein R is an alkyl radical containing from about 10 to about 18 carbon atoms and R and R are each selected from the group consisting of methyl, ethyl and propyl radicals, the ratio of alkyl benzene sulfonate to tertiary amine oxide being in the range of about 10:1 to about 1:2.

2. The composition of claim 1, wherein R and R are methyl radicals and R is a straight saturated chain of from 12 to 16 carbon atoms.

3. The composition of claim 1 wherein R and R are ethyl radicals and R is a straight saturated chain of from 12 to 16 carbon atoms.

4. A mild liquid detergent composition consisting essentially of about 5% to about 50% of the mixture of claim 1 in an aqueous vehicle.

5. A mild granular detergent composition consisting essentially of about 5% to about 50% of the mixture of claim 1, sodium tripolyphosphate and sodium sulfate.

6. The composition of claim 2 wherein R is a lauryl radical.

7. A mild liquid detergent composition consisting essentially of about 5% to about 50% of the mixture of claim 2, water and ethanol.

8. The composition of claim 3 wherein R is a lauryl radical.

9. The composition of claim 6 wherein the alkyl benzene sulfonate is sodium dodecyl benzene sulfonate.

10. A composition capable of synergistic mildness when used as an active ingredient in a detergent composition, said composition being a mixture of about equal parts of sodium dodecylbenzene sulfonate and lauryl dimethyl amine oxide.

11. A detergent composition consisting essentially of a mixture of about equal parts of a water soluble dodecyl benzene sulfonate and dodecyl dimethyl amine oxide, said mixture being capable of synergistic mildness.

References Cited by the Examiner UNITED STATES PATENTS 2,060,568 11/1936 Graenacher et al. 260583 XR 2,169,976 8/1939 Guenther et al. 260-4045 2,477,383 7/1949 Lewis 252161 FOREIGN PATENTS 437,566 10/1935 Great Britain. 503,047 5/ 1954 Canada.

OTHER REFERENCES The Chemistry of Fatty Amines, pub. by Armour and Co., 1948, page 13.

JULIUS GREENWALD, Primary Examiner. 

1. A COMPOSITION CAPABLE OF SYNERGISTIC MILDNESS WHEN USED AS AN ACTIVE INGREDIENT IN A DETERGENT COMPOSITION, SAID COMPOSITION BEING A MIXTURE OF A WATER SOLUBLE ALKYL BENZENE SULFONATE HAVING AN ALKYL RADICAL RANGING FROM ABOUT 9 TO ABOUT 15 CARBON ATOMS AND A TERTIARY AMINE OXIDE HAVING THE FORMULA R1R2R3->O WHEREIN R1 IS AN ALKYL RADICAL CONTAINING FROM ABOUT 10 TO ABOUT 18 CARBON ATOMS AND R2 AND R3 ARE EACH SELECTED FROM THE GROUP CONSISTING OF METHYL, ETHYL AND PROPYL RADICALS, THE RATIO OF ALKYL BENZENE SULFONATE TO TERTIARY AMINE OXIDE BEING IN THE RANGE OF ABOUT 10:1 TO ABOUT 1:2.
 5. A MILD GRANULAR DETERGENT COMPOSITION CONSISTING ESSENTIALLY OF ABOUT 5% TO ABOUT 50% OF THE MIXTURE OF CLAIM 1, SODIUM TRIPOLYPHOSPHATE AND SODIUM SULFATE. 